Visible-light photooxidation of water to oxygen at hybrid TiO2 -polyheptazine photoanodes with photodeposited Co-Pi (CoO(x)) cocatalyst.

A cobalt oxide-based oxygen-evolving cocatalyst (Co-Pi) is photodeposited by visible-light irradiation onto nanocrystalline TiO(2)-polyheptazine (TiO(2)-PH) hybrid photoelectrodes in a phosphate buffer. The Co-Pi cocatalyst couples effectively to photoholes generated in the surface polyheptazine layer of the TiO(2)-PH photoanode, as evidenced by complete photooxidation of water to oxygen under visible-light (λ>420 nm) irradiation at moderate bias potentials. In addition, the presence of the cocatalyst also reduces significantly the recombination of photogenerated charges, particularly at low bias potentials, which is ascribed to better photooxidation kinetics resulting in lower accumulation of holes. This suggests that further improvements of photoconversion efficiency can be achieved if more effective catalytic sites for water oxidation are introduced to the surface structure of the hybrid photoanodes.

Chemistry of SURMOFs: layer-selective installation of functional groups and post-synthetic covalent modification probed by fluorescence microscopy.

Layer-selective installation of functional groups at SURMOFs (surface-attached metal-organic framework multilayers) is reported. Multilayers of [Cu(ndc)(dabco)(0.5)] grown in [001] orientation on pyridine-terminated organic self-assembled monolayers on Au substrates were functionalized with amino groups by step-by-step liquid-phase epitaxy. The method allows the growth of samples exhibiting one monolayer of functional groups at the external thin-film surface. In situ quartz crystal microbalance monitoring confirmed the presence of amino groups by turning the multilayer film from a non-reactive to a reactive material for covalent binding of fluoresceinisothiocyanate, and fluorescence microscopy displays the expected luminous property.

Liquid-phase epitaxy of multicomponent layer-based porous coordination polymer thin films of [M(L)(P)0.5] type: importance of deposition sequence on the oriented growth.

The progressive liquid-phase layer-by-layer (LbL) growth of anisotropic multicomponent layer-based porous coordination polymers (PCPs) of the general formula [M(L)(P)(0.5)] (M: Cu(2+), Zn(2+); L: dicarboxylate linker; P: dinitrogen pillar ligand) was investigated by using either pyridyl- or carboxyl-terminated self-assembled monolayers (SAMs) on gold substrates as templates. It was found that the deposition of smooth, highly crystalline, and oriented multilayer films of these PCPs depends on the conditions at the early growth cycles. In the case of a two-step process with an equimolar mixture of L and P, growth along the [001] direction is strongly preferred. However, employing a three-step scheme with full separation of all components allows deposition along the [100] direction on carboxyl-terminated SAMs. Interestingly, the growth of additional layers on top of previously grown oriented seeding layers proved to be insensitive to the particular growth scheme and full retention of the initial orientation, either along the [001] or [100] direction, was observed. This homo- and heteroepitaxial LbL growth allows full control over the orientation and the layer sequence, including introduction of functionalized linkers and pillars.

Assessing the adsorption selectivity of linker functionalized, moisture-stable metal-organic framework thin films by means of an environment-controlled quartz crystal microbalance.

The stepwise thin film deposition of the robust, hydrophobic [Zn(4)O(dmcapz)(3)](n) (dmcapz = 3,5-dimethyl-4-carboxy-pyrazolato) is reported. The adsorption of small organic probe molecules, including alkanols, toluene, aniline and xylenes, was monitored by an environment-controlled quartz crystal microbalance setup. The adsorption selectivity was tuned by introducing alkyl side chains in the dmcapz linker.

External forces control mitotic spindle positioning.

The response of cells to forces is essential for tissue morphogenesis and homeostasis. This response has been extensively investigated in interphase cells, but it remains unclear how forces affect dividing cells. We used a combination of micro-manipulation tools on human dividing cells to address the role of physical parameters of the micro-environment in controlling the cell division axis, a key element of tissue morphogenesis. We found that forces applied on the cell body direct spindle orientation during mitosis. We further show that external constraints induce a polarization of dynamic subcortical actin structures that correlate with spindle movements. We propose that cells divide according to cues provided by their mechanical micro-environment, aligning daughter cells with the external force field.